JPH0532340B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a calcium silicate molded body with significantly improved heat insulation performance and a method for producing the same. BACKGROUND ART Calcium silicate molded bodies are widely used in various fields because they are lightweight, have excellent heat insulation properties, have high fire resistance, and have many other properties. In recent years, in the fields of heat retaining materials, heat insulating materials, etc., there has been a demand for calcium silicate molded bodies with even higher heat insulation performance. DISCLOSURE OF THE INVENTION The present invention satisfies the above-mentioned main points, and its purpose is to provide a calcium silicate molded body with significantly improved heat insulation performance. As a result of intensive research, the present inventor discovered that the above object can be achieved by incorporating an inert compound of rare earth elements, which has never been blended into a calcium silicate molded product, into a calcium silicate molded product. The invention was completed. That is, the present invention provides a calcium silicate molded body characterized by containing an inert compound of a rare earth element. The calcium silicate molded article of the present invention is constituted by a calcium silicate crystal molded article containing an inert compound of a rare earth element, thereby significantly improving the heat insulation performance. The inactive compound of a rare earth element in the molded article of the present invention means a rare earth element compound that is chemically inert to the formation reaction of calcium silicate crystals, and specific preferred compounds include, for example, cerium oxide, yttrium oxide, Oxides such as neodymium, lanthanum oxide, samarium oxide, gadolinium oxide, praseodymium oxide, dysprosium oxide, ytterbium oxide, erbium oxide, holmium oxide, europium oxide, cerium hydroxide, yttrium hydroxide, neodymium hydroxide, lanthanum hydroxide, Hydroxides such as praseodymium hydroxide, ytterbium hydroxide, erbium hydroxide, terbium hydroxide, cerium carbonate, ythtrium carbonate, neodymium carbonate, lanthanum carbonate, praseodymium carbonate, dysprosium carbonate, yzterbium carbonate, erbium carbonate, terbium carbonate, etc. carbonate, cerium oxalate, yttrium oxalate, neodymium oxalate, lanthanum oxalate, gadolinium oxalate, praseodymium oxalate,
Examples include oxalates such as dysprosium oxalate, ytterbium oxalate, erbium oxalate, niobium oxalate, europium oxalate, and thulium oxalate.
In the present invention, at least one inert compound of a rare earth element is contained. The content of the rare earth element inert compound in the molded article in the present invention can be selected from a wide range, but
The appropriate amount is usually about 2 to 60% by weight, preferably about 5 to 50% by weight of the total solid content of the molded article. Outside this range, the improvement in heat insulation performance tends to be insufficient. The molded article of the present invention can be produced by adding an inert compound of a rare earth element at any stage of the production process in various known methods for producing calcium silicate molded articles. That is, the present invention provides: (A) A raw material slurry containing a silicate raw material, a lime raw material, and water is subjected to a hydrothermal synthesis reaction while being heated and stirred under pressure to prepare an aqueous slurry of calcium silicate crystal secondary particles, and then this is molded. , a method for producing a calcium silicate molded body by drying, the method comprising adding an inert compound of a rare earth element to a raw material slurry or an aqueous slurry of calcium silicate crystal secondary particles; (B) An aqueous slurry of calcium silicate crystal precursor is prepared by preliminarily reacting a raw material slurry containing a silicate raw material, a lime raw material, and water while heating and stirring under normal pressure or pressure, and then molding this. In a method for producing a calcium silicate molded body by steam curing and drying the resulting formed body,
The present invention also provides a method for producing a calcium silicate molded body, characterized in that an inert compound of a rare earth element is added to a raw material slurry or an aqueous slurry of a calcium silicate crystal precursor. The above production method (A) of the present invention is a slurry of a raw material slurry before a hydrothermal synthesis reaction in which an inert compound of a rare earth element (hereinafter simply referred to as a rare earth compound) is stirred, or a slurry of secondary particles of calcium silicate crystals after the reaction. Basically, a raw material slurry containing a silicic acid raw material, a lime raw material, and water described in Japanese Patent Publication No. 45-25771 is subjected to a hydrothermal synthesis reaction while heating and stirring under pressure to produce calcium silicate crystals. This method is similar to the method for producing a calcium silicate molded body by preparing an aqueous slurry of secondary particles, then molding and drying the slurry. This method has the advantage that the obtained molded product has high strength because the calcium silicate crystals form secondary particles. As the silicic acid raw material used in the present invention, any of those conventionally used in the production of calcium silicate molded bodies can be effectively used. Examples of raw materials include silica gel, silica flour (ferrosilicon dust, etc.), white carbon, diatomaceous earth, and silica obtained by reacting hydrosilicic acid and aluminum hydroxide, which are by-produced in the wet phosphoric acid production process. Furthermore, any lime raw material that has been used conventionally can be used, and examples include quicklime, slaked lime, and carbide slag. Moreover, the CaO/SiO ₂ molar ratio of the silicic acid raw material and the lime raw material is usually about 0.5 to 1.5. For example, if you are trying to synthesize tobermolite crystal, it is 0.70 to 0.90.
It is preferable to set it to about 0.90 to 1.15 when trying to synthesize xonotlite crystals, and about 1.1 to 1.5 when trying to synthesize phosciaite crystals. In the production method (A) of the present invention, a raw material slurry is prepared by adding a rare earth compound to the silicic acid raw material, lime raw material, and water, or to these. Conventionally known additives may be added to the raw material slurry, and examples of additives in this case include inorganic fibers such as asbestos and rock wool. The amount of water when preparing the raw material slurry is at least 5 times the solid content of the raw material slurry, preferably 10 to 50 times the weight, and when producing a lightweight body with a density of about 0.1 g/ ^cm3 , the amount of water is 15 times the solid content of the raw material slurry. It is appropriate that the amount be 50 times by weight, preferably 20 to 40 times by weight. The raw material slurry thus prepared is then subjected to a hydrothermal synthesis reaction while being stirred. This reaction is carried out under a saturated steam pressure of usually 4 kg/cm ² or higher, preferably 6 to 30 kg/cm ² . Through this reaction, calcium silicate crystals such as tobermolite crystals, xonotrite crystals, and phosiyaite crystals are the main components,
Secondary particles with an outer diameter of approximately 5 to 150 μm are generated in which these particles are three-dimensionally entangled, and a slurry in which these particles are uniformly dispersed in water is obtained. In addition, when a rare earth compound is added to the raw material slurry, the coexisting rare earth compound is physically integrated with the calcium silicate crystal secondary particles in a state of being wrapped in the secondary particles, and this is uniformly dispersed in water. A slurry is obtained. In the production method (A), when the rare earth compound is not added to the raw material slurry, the rare earth compound is added to the aqueous slurry of the calcium silicate crystal secondary particles and mixed uniformly. In the production method (A), the rare earth compound is more preferably added to the raw material slurry before the hydrothermal synthesis reaction. As a result, the rare earth compound is physically integrated with the calcium silicate crystal secondary particles produced, as described above, so that the strength reduction of the obtained molded product is extremely small. The amount of the rare earth compound added is not particularly limited, but the content in the molded product is usually 2% in the total solid content of the molded product.
It is appropriate to set the amount to about 60% by weight, preferably about 5 to 50% by weight. In addition, the rare earth compound used is usually in the form of powder, and its particle size is usually about 0.001 to 120 μm, preferably 0.001 to 120 μm.
Approximately 100 μm is appropriate. Next, the aqueous slurry of calcium silicate crystal secondary particles containing the rare earth compound obtained above is molded. At this time, prior to molding, various additives may be further added and mixed as necessary. As additives in this case, those that have been used in the production of calcium silicate molded bodies can be used in a wide range.
Examples include fibers, clays, cement, and various binders. The molding method may be a conventional method such as press dehydration molding, centrifugal dehydration molding, etc. Next, the desired calcium silicate molded body is obtained by drying. In addition, during molding, if necessary, the aqueous slurry containing the rare earth compound obtained above is placed in a mold and press-dehydrated, and then a calcium silicate crystal slurry free of rare earth compounds obtained by a conventional method is placed on top of it. Either put it in a mold and press dehydrate it, or
Alternatively, a laminate molded product can be obtained by performing the reverse operation. Calcium silicate molded bodies obtained by manufacturing method (A) can be easily manufactured from high density to low density ones, but especially low-density lightweight molded bodies, such as bulk density of about 0.1 g/cm ³ , can be easily produced. When producing it, it is preferable to use milk of lime with a sedimentation volume of 5 ml or more. Particularly preferred are those with a sedimentation volume of 10 ml or more. The sedimentation volume of milk of lime refers to the sedimentation volume of lime particles after 50ml of milk of lime with a water to lime solids ratio of 120 times is left to stand for 20 minutes in a graduated cylinder with an inner diameter of 1.3cm and a volume of ^50cm3 . The volume is shown in ml.
A large sedimentation volume means that lime is well dispersed in water, stable, and highly reactive. By using milk of lime with a large sedimentation volume, the apparent density of the obtained secondary particles of calcium silicate crystals becomes low, making it easy to produce a low-density, lightweight body. The production method (B) of the present invention basically consists of
41-1953 or Japanese Patent Publication No. 58-30259, a raw material slurry containing a silicic acid raw material, a lime raw material, and water is preliminarily reacted with heating and stirring under normal pressure or increased pressure to form an aqueous calcium silicate crystal precursor. This method is similar to the method for producing a calcium silicate molded body by preparing a slurry, then molding the resulting molded body, and steam-curing and drying the resulting molded body. In production method (B), the same raw material slurry as in production method (A) is preliminarily reacted to prepare an aqueous slurry of calcium silicate crystal precursor. Calcium silicate crystal precursors refer to various intermediates when calcium silicate crystals are generated from silicate raw materials and lime raw materials, such as calcium silicate gel, C-S-H
(), C-S-H(), and the like.
The method for obtaining the precursor is, for example, by heating the above raw material slurry to about 80 to 98°C under normal pressure and reacting it,
Alternatively, it is usually carried out by carrying out a hydrothermal synthesis reaction under a saturated steam pressure of 3 kg/cm ² or more. This provides an aqueous slurry of calcium silicate crystal precursor. When the rare earth compound is not added to the raw material slurry in production method (B), the rare earth compound is added to the aqueous slurry of the precursor and mixed uniformly.
The amount of rare earth compound added, particle size, etc. are the same as in production method (A). Next, the aqueous slurry of the calcium silicate crystal precursor containing the rare earth compound obtained above is molded in the same manner as in production method (A) to obtain a formed body of the precursor. Next, the green body obtained above is subjected to steam curing. Steam curing is carried out to convert the calcium silicate crystal precursor in the formed body into calcium silicate crystals, and is carried out under a saturated steam pressure of usually 4 Kg/cm ² or more, preferably 6 to 30 Kg/cm ² . Next, the desired calcium silicate molded body is obtained by drying. In addition, during the molding, if necessary, laminated molding can be performed by molding in two steps in the same manner as above using an aqueous slurry of calcium silicate crystal precursor containing a rare earth compound and the slurry not containing a rare earth compound. You can also get a body. BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically explained below by showing examples. However, parts and percentages in the following examples indicate parts by weight and percentages by weight, respectively, and various physical properties were measured by the following methods. (a) Bending strength: Measured according to the method of JIS A9510. (b) Thermal conductivity...Measured according to the cylinder method of JIS A9510. Example 1 Quicklime (95% CaO) was slaked in warm water at 80°C,
The settling volume of the milk of lime obtained by dispersing it in water using a homomixer was 17 to 22 ml. CaO/silica powder (SiO ₂ 94%) with an average particle size of 6.5 μm is added to the above lime milk.
Add SiO so that the molar ratio of ₂ is 1.00, and add water,
Alternatively, a predetermined amount of rare earth compound powder and water were added and mixed so that the total amount of water was 15 times the weight of the solid content to obtain a raw material slurry. This was stirred in an autoclave at a saturated water vapor pressure of 12 Kg/cm ² and a temperature of 191°C with a stirring blade rotating at a rotation speed of 40 rpm.
A slurry of calcium silicate crystals was obtained by conducting a hydrothermal synthesis reaction for a period of time. When the crystal slurry obtained above was dried at 100°C for 24 hours and subjected to X-ray diffraction analysis, xonotrite crystals were observed in all slurries, and a peak of the compound was observed in those containing rare earth compounds. . In addition, when these crystal slurries were observed using an optical microscope and a scanning electron microscope, all slurries showed spherical shell-shaped secondary particles with an outer diameter of 5 to 150 μm formed by three-dimensional entanglement of xonotrite crystals. was recognized. In addition, in the case where a rare earth compound was added, it was observed that the compound was encapsulated in the secondary particles of xonotlite crystals and physically integrated with them. Next, 7 parts of glass fiber and 3 parts of Portland cement were added to 90 parts (solid content) of the crystal slurry obtained above.
A cylindrical molded product having an inner diameter of 114 mm, a thickness of 50 mm, and a length of 610 mm was obtained by press dehydration molding and drying at 100° C. for 24 hours. The physical properties of the obtained molded product were as shown in Table 1.

【table】

[Table] In Table 1, the molded bodies according to the present invention are samples No. 2 to 10.
and 12, and samples No. 1 and 11 are shown for comparison. From Table 1, the molded bodies No. 2 to 10 and 12 obtained by adding rare earth compounds to the raw material slurry according to the present invention have a
It is clear that the thermal conductivity is significantly reduced and the decrease in strength is very small. Example 2 90 parts (solid content) of calcium silicate crystal slurry obtained in the same manner as in Example 1 using a raw material slurry without the addition of rare earth compounds, 7 parts of glass fiber, 3 parts of Portland cement, or these and rare earth compounds. Example 1 by adding powder and press dehydration molding
A molded body having the same shape was obtained. The physical properties of each molded article obtained were as shown in Table 2.

[Table] From Table 2, containing the rare earth compound of the present invention
It is clear that the thermal conductivity of the molded bodies No. 14 to 21 is significantly lower than that of the comparative molded body No. 13 which does not contain the compound. Example 3 A raw material slurry with no rare earth compound added was prepared in the same manner as in Example 1 except that the total amount of water was 30 times the weight of ^the solid content.
A hydrothermal synthesis reaction was carried out in an autoclave at 200° C. for 2 hours while rotating a stirring blade at a rotational speed of 40 rpm to obtain an aqueous slurry containing C-S-H () as a main component. Next, 7 parts of alkali-resistant glass fiber, 3 parts of Portland cement, or a predetermined amount of these and the same cerium oxide powder as in Example 2 were added to 90 parts (solid content) of the slurry obtained above and molded. A molded body of the same shape was obtained. This molded body was steam cured for 3 hours at a saturated steam pressure of 15 kg/cm ² and then dried at 100°C. When the obtained compact was analyzed by X-ray diffraction, a peak of cerium oxide was observed in the case where xonotrite crystals and cerium oxide powder were added. The physical properties of each molded body were as shown in Table 3.

[Table] From Table 3, containing the rare earth compound of the present invention
It is clear that the thermal conductivity of the molded bodies No. 23 to 25 is significantly lower than that of the comparative molded body No. 22 which does not contain the compound. Example 4 Yttrium oxide powder (average particle size
A raw material slurry in which a predetermined amount of C-S-H (1.8 μm) was added to the molded body was subjected to a hydrothermal synthesis reaction in the same manner as in Example 3, and oxidized with C-S-H () or C-S-H (). An aqueous slurry containing yttrium as a main component was obtained. Next, 7 parts of alkali-resistant glass fibers were added to 93 parts (solid content) of the slurry obtained above, and press dehydration molding was performed to obtain a molded product having the same shape as in Example 1. This molded body was steam cured for 3 hours at a saturated steam pressure of 15 kg/cm ² and then dried at 100°C. When the obtained compact was analyzed by X-ray diffraction, an additional peak of yttrium oxide was observed in the product to which xonotlite crystals and yttrium oxide powder were added. The physical properties of each molded body were as shown in Table 4.

【table】

[Table] From Table 4, containing the rare earth compound of the present invention
It is clear that the thermal conductivity of the molded bodies No. 28 and 29 is significantly lower than that of the comparative molded bodies No. 26 and 27 which do not contain the compound.

Claims (1)

[Claims] 1. A calcium silicate molded article containing an inert compound of a rare earth element. 2. The molded article according to claim 1, wherein the rare earth element inert compound is at least one of oxides, hydroxides, carbonates, and oxalates. 3. The molded article according to claim 1, wherein the content of the rare earth element inert compound is 2 to 60% by weight based on the total solid content of the molded article. 4 A raw material slurry containing a silicate raw material, a lime raw material, and water is subjected to a hydrothermal synthesis reaction while being heated and stirred under pressure to prepare an aqueous slurry of calcium silicate crystal secondary particles, which is then molded and dried to form a calcium silicate mold. 1. A method for producing a calcium silicate molded body, which comprises adding an inert compound of a rare earth element to a raw material slurry or an aqueous slurry of calcium silicate crystal secondary particles. 5 A raw material slurry containing a silicic acid raw material, a lime raw material, and water is preliminarily reacted with stirring under normal pressure or pressure to prepare an aqueous slurry of a calcium silicate crystal precursor, and then this is obtained by molding. A method for producing a calcium silicate molded body by steam curing and drying the formed body, which is characterized in that an inert compound of a rare earth element is added to a raw material slurry or an aqueous slurry of a calcium silicate crystal precursor. Manufacturing method.